BOOKS OF THE TIMES

BOOKS OF THE TIMES; Through Ancient Eyes, a Glimpse of a Lost World

By RICHARD BERNSTEIN

Published: November 13, 2000

TRILOBITE!

Eyewitness to Evolution

By Richard Fortey

Illustrated. 287 pages. Alfred A. Knopf. $26.

The exclamation point on ''Trilobite!,'' the new book by the British paleontologist Richard Fortey, could merely reflect a private enthusiasm, that of a scientist for his domain of research. But certainly Mr. Fortey, whose previous book was ''Life: A Natural History of the First Four Billion Years of Life on Earth,'' means to indicate something more than an arcane interest.

His ''Trilobite!'' is a history of the study of an extinct crustacean and what we can learn from it. It turns out that we can learn a great deal, especially when our instructor is as knowledgeable and engaging a figure as Mr. Fortey.

He starts with a visit to a scene in ''A Pair of Blue Eyes,'' a novel by Thomas Hardy, in which his protagonist is dangling from the Beeny Cliff in Cornwall, England, and sees a trilobite fossil staring back at him: a kind of interspecies communication across a gulf of half a billion years. Mr. Fortey ends with some reflections on the measurement of geological time. In between is a melange of subjects and themes, all of them loosely connected by the study of fossils and rocks and bearing on big questions: the creation of a world in which sight dominates the other senses; the actual workings of evolution; what fossils tell us about the formation of ancient oceans and continents.

Mr. Fortey's text moves slowly in places, and his enthusiasm for trilobites provides an amount of information that some with less enthusiasm might find hard to assimilate. But give me a scientist with a sense of humor and a knack for metaphor who also happens to have an encyclopedic understanding of natural history, and I will always be happy. Mr. Fortey is such a writer.

''The deep language of the genes is an Esperanto of biological design which can be understood by a Babel of organisms,'' he writes at one point about the genetic origins of eyes. And later, in a passage about the bottled zoological collections of natural history museums: ''Color fades, so that the ghostly quality of spirit preservation seems to match the antiquity of the specimens. As you slide the doors back upon this pallid parade of containers and bottles your voice automatically loses decibels. You reflect: mortality, this is your sad face; you defy decay only as a ghastly pickle.''

Trilobites are among the most commonly found fossils lying in the geological rock, the slates and sandstones formed hundreds of millions of years ago on former ocean beds. There was an enormous variety of them, swimmers and crawlers and burrowers, as large as a crab or as tiny as a pumpkin seed. They inhabited the seas for about 300 million years, which is about 150 times as long as humankind has survived so far, and that fact alone imparts to Mr. Fortey's book some of the sense of wonder that saturates it. His purpose is, as he puts it, ''to see the world through the eyes of fossils as a means to animate the past.''

Seeing is a vital concept here, because one of the illuminations that the study of trilobites provides has to do exactly with the origins of the metaphor wherein to see means to understand. The development of the eye was not, Mr. Fortey argues, an evolutionary inevitability. The eyes of trilobites, which are compound and formed from crystal, demonstrate that the path of ''sophisticated sight'' was the one that happens to have been taken; it was ''an innovation that made the world visible.''

The trilobites were not the first organisms to develop eyes, and therefore to develop what Mr. Fortey calls the gene that says, ''Make eyes!'' But they are old enough to prove that those genes, which are elements in the human inheritance, ''must be so ancient that they go back before the last common ancestor of insect and vertebrate.'' Mr. Fortey has a typically whimsical way of expressing this:

'' 'Look into my eyes,' the trilobite seems to say, 'and you will see the vestiges of your own history.' '' And more, by knowing the eyes of the trilobite, we can comprehend the way those animals comprehended their world. ''For us to see that the trilobites once saw, too, is to bring them within the compass of our own understanding,'' Mr. Fortey writes.

He exploits the defunct trilobite to survey several other matters in evolutionary history. He summarizes, for example, the work of Niles Eldredge, a scholar at the American Museum of Natural History whose painstaking research on the eyes of trilobites led him to the concept of ''punctuated equilibrium,'' which is a model for the way evolution actually works. It means essentially that species endure for a long time and then for some reason are suddenly replaced by a new species.

He takes time to tell the tragic story of a gifted young German scientist named Rudolf Kaufmann who wrote an obscure paper that described punctuated equilibrium by another name some 40 years before Mr. Eldredge did. Kaufmann, who was born a Jew, was shot by the Nazis in 1941.

Among the most fascinating passages in ''Trilobite!'' are the ways in which the study of fossils and a branch of geology called paleomagnetics has enabled researchers to draw maps of various possible geological worlds, when Africa and South America were part of the same continent, and Wales was a peninsula off the coast of Newfoundland. ''Map the trilobites and you map the continent,'' Mr. Fortey writes.

Reading this book, one begins to understand the reasons for Mr. Fortey's exclamation point, and for his own absorption over 30 years in the study of a spiny little sea creature that died out 180 million years before the dinosaurs. ''Trilobite!'' is a demanding book at times, since while Mr. Fortey writes for nonspecialists, he steadfastly avoids reducing the complexity of things. But it is of the genre of the best science writing, wherein careful observation and tremendous ingenuity by generations of scientists are shown to generate large ideas, grand ideas, ideas with implications for the way we see ourselves and our place in universal history.